According to a witness to the shooting and to Byron Goode, 50, Mr. Jones’s brother, there had been rising tensions between youngsters living at Risley Dent Towers and youths from a gang at a building nearby.

Mr. Jones, who had friends at Risley Dent Towers, had recently broken up a confrontation between the groups of youths outside the development, according to the witness, who would not give his name out of fear of retribution, and Mr. Goode.

“He told them it was senseless and meaningless,” Mr. Goode said, “and that they should not be there and they’d wind up in jail.” He said he thought Mr. Jones might have been shot in retaliation for getting involved, but the police said they were still investigating the motive.

The wounded man was in stable condition at Interfaith Medical Center, the police said.

Mr. Jones lived with Mr. Goode and their mother in a neatly kept apartment a block from the scene of the shooting, and yesterday it was filled with mourning relatives and friends.

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A second shooting occurred at 2:30 a.m. at Park Place and Ralph Avenue in the Crown Heights neighborhood of Brooklyn, the police said, when a man, age 35, was shot in the chest, leg and shoulder by someone in a passing vehicle.

The victim, whose name was not released, was taken to Kings County Hospital Center in critical condition, they said.

Forty minutes later, outside 105 Winthrop Street in Prospect Lefferts Gardens in Brooklyn, a group of men surrounded a 30-year-old man and stabbed him several times, the police said. The victim, whose name was not released, was also taken to Kings County Hospital Center in critical condition, they said.

A fourth attack occurred about 4 a.m. in front of 523 West 157th Street in Manhattan, the police said. A 35-year-old man, whom the police identified as Barbaro Pallet, was walking with a female companion when another man approached.

The two men began arguing, the police said, and the second man pulled out a gun and shot the man several times, killing him, and then fled, the police said. The police said the female companion was “severely intoxicated” at the time and was not cooperating with the investigation.

Yesterday evening two other men were killed in separate incidents in Queens and the Bronx.

Antoine Alverez, 19, was found by the police at about 7:40 p.m. with a gunshot wound in the back at 147th Avenue and Springfield Boulevard in the Springfield Gardens section of Queens.

About half an hour earlier in the Bronx, a 19-year-old man was found dead with a gunshot wound to the chest in front of 355 East 187th Street in the Fordham section. The man has not been identified pending notification of his relatives.

Ann Farmer and Timothy Williams contributed reporting.

A version of this article appears in print on , on Page A31 of the New York edition with the headline: 6 Attacks in City Leave 4 Dead and 2 Critically Wounded. Order Reprints|Today's Paper|Subscribe